We've all heard that milk does a body good, but so do all dairy products, green leafy vegetables, broccoli, and other foods that are rich in calcium. A key building block for strong, healthy bones, calcium is critical during childhood and adolescence. But most kids ages 9 to 18 don't get the recommended 1,300 mg of calcium per day.

Calcium plays a role in blood clotting, heart rhythm, nerve transmission, muscle growth, the release of hormones and enzymes, and proper functioning of the cell membranes. However, less than 1 percent of total body calcium is needed to support these functions. The remaining 99 percent of the body's calcium supply is stored in the bones and teeth.

We all need adequate calcium from infancy through adulthood, but it's during childhood through the end of the teen years that the body uses this mineral to build a strong skeletal foundation that will carry us through our lives.

Bone goes through a continuous process of remodeling, with constant resorption and deposition of calcium into new bone. During periods of growth in kids, bone formation exceeds resorption. In early adulthood, the processes are relatively equal. But as we get older, particularly around menopause in women, bone breakdown exceeds formation, resulting in bone loss that increases the risk of osteoporosis.

Teenagers, particularly girls, whose diets don't provide enough calcium to build bones to their maximum potential, are at greater risk of developing osteoporosis later in life. Babies and younger children who don't get adequate calcium and vitamin D (which is essential for calcium absorption) are at risk for developing rickets, a disease that causes softening of the bones and severely bowed legs, poor growth, and muscle weakness.

Kids need a combination of calcium, vitamin D, and physical activity during childhood and the teen years to build the strongest bones possible. In addition to dairy and leafy greens, tofu, salmon, and chickpeas are good sources of calcium, as are calcium-fortified foods like soymilk, orange juice, and some cereals.

A high-quality multivitamin supplement specially formulated for kids will also provide calcium, vitamin D, and other bone-building vitamins and minerals. Calcium is also available as an individual supplement. Look for a children's calcium formula that contains vitamin D3 or cholecalciferol, the most active form of the vitamin